soda ash vs cholorine use

I am going broke on cholorine use.
I have a 35,000 gallon in ground vinel liner pool I live in north TX were temp in summer is about 90-110.I run the pump for about 16 hours a day.My question is I have 3 cholorine floats and need to fill them about every 3 days.In addition I put a tab in each skimmer (2).I do get alage if I let them get low because of the sun that shines about 13 hours a day.Can a lack of soda ash cause the choline demand to be high?
It seems that my pool needs more soda ash then my dads pool in CA.His is a gunite pool.
I need help at about 70 bucks a pail for cholorine I am sinking fast.

Thanks for that good info I will check the PH when I get home today.When you say effective does this also mean how fast a 3 inch tab dissolves.Or is does that have to do with the water temp?In the winnter tabs last a lot longer.